Well if you guessed “newspaper stunt adapted from a Christian holiday but with ancient pagan roots too”, award yourself 10 points.
The first Groundhog Day in America was a newspaper stunt in 1887:
The first Groundhog Day celebration in Punxsutawney was the brainchild of local newspaper editor Clymer Freas, who sold a group of businessmen and groundhog hunters—known collectively as the Punxsutawney Groundhog Club—on the idea.
Who knew that there were groups of “businessmen and groundhog hunters”? I sure didn’t.
In any case German settlers in the area brought it with them from the homeland, where the Germans had adapted it from an ancient Christian celebration called Candlemas.
What is Candlemas?
Wikipedia says it’s about bringing the baby Jesus, just a few weeks old, to the temple for purification:
It is based upon the account of the presentation of Jesus in Luke 2:22–40. In accordance with Leviticus 12, a woman was to be purified by presenting a lamb as a burnt offering, and either a young pigeon or dove as sin offering, 33 days after a boy's circumcision. It falls on 2 February, which is traditionally the 40th day (postpartum period) of and the conclusion of the Christmas–Epiphany season. While it is customary for Christians in some countries to remove their Christmas decorations on Twelfth Night (Epiphany Eve), those in other Christian countries historically remove them after Candlemas. On Candlemas, many Christians (especially Eastern Orthodox, Roman Catholics, Lutherans, Anglicans and Methodists) also take their candles to their local church, where they are blessed and then used for the rest of the year; for Christians, these blessed candles serve as a symbol of Jesus Christ, who is the Light of the World.
If you’re now wondering how in 1400 years a Christian holiday evolved from purifying the baby Jesus at the temple to “let’s use a rodent to predict the weather”, you’re not alone.
But wait, there’s more!
February 2 is basically (almost but not quite) the midpoint between the Winter Solstice and Spring Equinox, and so of course there was a pagan ritual associated with it: Imbolc dates back to the 10th century BC among the Celtic people, celebrating both the the midpoint of Winter and a Celtic goddess Brigid who later became a saint in the Catholic church.